Dilatable balloon implant

ABSTRACT

The invention relates to a dilatable balloon implant, which is configured with a limited permeability to liquid. The invention also relates to a vertebroplasty device comprising a balloon implant with a limited permeability to liquid, which is connected to the distal end of an introduction sleeve in such a way that the interior of said implant communicates with the introduction sleeve lumen.

The invention relates to a dilatable balloon implant. The invention alsorelates to a device for placing such an implant in bone cavities.

A known method for treating vertebra factures (caused in particular as aresult of osteoporotic changes in bone tissue) consists in directlyfilling bone cement or another filler material via a percutaneous accesstract into the vertebra and stabilizing it in this manner(vertebroplasty). This method has a disadvantage in that the vertebracannot be erected prior to stabilization. Moreover, this method involvesthe risk of filler material exiting from the inner vertebra cavity andentering the body.

Moreover, filler material may also enter the spinal channel, theneuroforamen or the venous plexus of the vertebra and obstruct thelatter or get carried away with the bloodstream, thus causing emboliesor infarctuses. This method involves the particular problem that therisk of material exiting the vertebra cavity increases if the viscosityof the filler material is too low, while—in the case of the viscositybeing too high—the material hardens too quickly, which in turn leads toan inadequate filling.

According to a further state-of-the-art treatment method, the spongiosaof the vertebra is compressed and thus expanded, using one or severalballoon catheters (cyphoplasty), before the cavity is filled with fillermaterial. This method serves, on the one hand, to seal cracks in orderto prevent the potential escape of filler material and, on the otherhand, to potentially erect the vertebra before the filler material isintroduced. The need, associated with this method, to remove the ballooncatheter extends the length of the surgical intervention and holds therisk of the tonus of the back muscles undoing a previously performederection. Moreover, cyphoplasty cannot completely prevent fillermaterial entering the spinal channel, a neuroforamen or the venousplexus.

In view of the problems connected with the state-of-the-art treatment ofvertebra fractures, the objective of the invention is to provide animplant that minimizes the risk of filler material exiting duringvertebroplasty while keeping the intervention time as short as possibleand which enables the erection of the vertebra.

According to the invention, this objective is achieved by the use of aballoon implant of the type described above, which provides limitedliquid permeability.

The balloon implant according to the invention is introduced, indeflated condition, into the prepared (i.e. opened) vertebra through apercutaneous access tract using a tube-shaped introduction sleeve. Onceplaced inside the vertebra, the balloon implant is dilated, preferablyby introducing a filler material through the introduction sleeve. Thelimited liquid permeability ensures, on the one hand, that the risk offiller material entering the spinal channel is minimized and enables, onthe other hand, a safe connection to be achieved between the implant andthe bone. This permits the use of filler material with a lower viscositythan is used in state-of-the-art treatment methods, thus eliminatingalso the risk of the filler material hardening before the vertebracavity is completely filled. Moreover, the pressure exerted as theballoon is dilated permits the vertebra to be erected, if so desired.

After the cavity has been filled, the proximal inflow opening of theimplant is closed, and the implant is separated from the introductionsleeve.

The use of the implant as described by this invention leads to a bettertherapy result than that obtained with state-of-the-art operationmethods in that it minimizes the complications related to excessiveleakage of filler material and overly long intervention times.

In its simplest embodiment, the implant consists only of the balloonproper, though it may also be provided with further elements (e.g.joining elements). In this case, only the balloon proper needs to havelimited liquid permeability.

The balloon may consist of a material that has limited liquidpermeability or of a liquid impermeable material that is provided withpores that impart limited liquid permeability to the balloon.

The materials may be elastic or non-elastic, provided they meet therequirements for medical materials in terms of physiologicalcompatibility and tear resistance. In a preferred embodiment, plasticmaterials are used, which can be kept particularly small forintroduction into the cavity, so that they can be used for instance withcatheters that have a particularly small cross section.

In a preferred embodiment, the liquid perrneable material is a textiletissue or fabric, notably a nylon tissue. Materials that meet therequirements of DIN Standard 53861-3 are especially suitable. Thedensity of the balloon material used must allow a limited amount ofliquid to leak out before the filler material hardens. A competentexpert can easily select a suitable balloon material for the specificfiller material employed.

A material that is particularly suitable as liquid impermeable materialwith pores is perforated or stippled latex, as that material is, ingeneral, physiologically tolerable and elastic.

The size and number of pores (i.e. the pore density) of the inherentlyliquid impermeable material are dependent on the filler material used(e.g. conventional bone cement or polymerizing filler materials) and canbe easily determined for a given filler material by a competent expert.For customary materials, a pore density of up to 5%, preferably 1 to 3%,related to the material surface, is especially suitable.

The pores are to be so dimensioned that, during therapy, bone fillermaterial exits an amount of 0.05 to 6, preferably 1 to 4, and especiallypreferably 2 to 3%, thus ensuring proper anchorage of the implant due toa high number of pores.

Materials (that are inherently water permeable or inherently waterimpermeable, but provided with pores) are especially suitable as balloonmaterials, if they guarantee permeability of the balloon to medical bonefiller material in the range of 0.05 to 6, preferably 1 to 4 andespecially preferably 2 to 3%.

These permeability levels denote the amount of filler materialintroduced in liquid condition that exits during the time until thefiller material has hardened inside the cavity, the total amount offiller material introduced into the balloon being 100%. Thus thematerial to be selected by the expert depends on the filler material tobe used and its viscosity. It is no problem for an expert to determinethe best suitable balloon material for the filler material used (lowerviscosity or slower hardening rate—higher material density).

The implant according to the invention permits the use of fillermaterial of particularly low viscosity (In which case a denser materialmust be used, so that the appropriate permeability levels as mentionedabove can be achieved), which significantly reduces the risk of fillermaterial hardening before the intervention is complete and also permitsthe use of small-bore introduction sleeves and other small-bore devices.Such low permeability levels minimize the operation risk related toexcessive leakage of filler material, while permitting the implant to besecurely fixed inside the vertebra cavity.

In non-dilated condition, the balloon assumes a bag-like shape. In anexpedient embodiment, it assumes, in dilated condition and without theaction of external constraints (e.g. the shape of the vertebra cavity),a predetermined form, which may be essentially ball-shaped orcuboid-shaped or even of more complex shape. Thus, for any vertebraconfiguration, a specifically adapted implant can be chosen, whichsafely ensures that the cavity is completely filled. This safety isenhanced by the use of elastic balloon materials, which guarantee aparticularly good adaptation of the dilated balloon shape to the shapeof the cavity.

In another expedient embodiment, the implant—for the purpose of beingseparated from the introduction means—is provided with a thinner wallarea at its proximal, open end, which functions as a predeterminedbreaking point. This especially low-cost variant enables the balloon tobe closed and the implant to be separated from the introduction deviceby means of a combined turning/slight pulling motion after the cavityhas been filled, so that the implant can be easily separated due to itspull reaction. (In this case, the access tract to the vertebra cavityshould have a smaller cross section than the cavity itself, so that theimplant, after being filled in, is kept safely in place by a mechanicalclamping action even before the material has hardened.)

In a further expedient embodiment, the implant is provided, in itsproximal area, with a joining element, which permits a separable andconductive connection to be formed between the implant and itsintroduction sleeve. Depending on what type of joining element is used,the implant is separated from the introduction sleeve from outside, e.g.by mechanical action, electrolytic detachment or by means of laserflashes. Such joining elements and the materials required to make themare known to competent experts.

Yet a further expedient embodiment is a design, in which the implant isprovided with a closing device for the proximal opening, which thesurgeon can operate from outside (e.g. a plug or a loop that can beclosed by exerting a pulling action).

The invention relates also to a vertebroplasty device with a balloonimplant according to any of the above claims, which is connected to thedistal end of an introduction sleeve, so that its interior communicateswith the introduction sleeve lumen. (Here the term “distal end” does notnecessarily mean the distal tip of the introduction sleeve, but thedistal end area.)

The implant can basically be joined to the introduction sleeve using anyof the known expedient techniques—thus the implant may be joined to theintroduction sleeve at the latter's external or internal circumferenceor the connection may take the form of a continuous transition from theimplant to the introduction sleeve.

An expedient solution is a device, in which the balloon is joined to theintroduction sleeve by a form-fit joining method, such as gluing,clamping expanding or bolting if necessary, the balloon and/or theintroduction sleeve is/are to be provided with suitable retainingelements.

Separability between the implant and the introduction sleeve is ensuredeither by a connection between the introduction sleeve and the balloonthat is itself separable (e.g. the above-mentioned bolting or clampingmethods or electrolytic separability of one or several joining elements)or by an inseparable connection between the introduction sleeve and theballoon, with the balloon being provided with a predetermined breakingpoint (see above).

An expedient device is a type of device, in which the open end of theballoon is secured to the inner circumference of the introductionsleeve.

According to a further, especially expedient embodiment, the open end ofthe balloon is pulled over the distal end of the introduction sleeve andsecured to the outer circumference of the introduction sleeve.

In an especially advantageous embodiment of the device, the introductionsleeve is provided, at its distal end, with a reinforcing element thatserves to strengthen the connection between the distal end of theintroduction sleeve end and the proximal end of the implant. It may bepart of the introduction sleeve wall (turned down distal end) or takethe form of an additional element (e.g. a ring), which is firmlyconnected to the introduction sleeve in a conventional manner.

The element is preferably designed as a clamp or press ring, which,acting as a stopper bead, firmly clamps the proximal end of the balloonto the introduction sleeve (thus providing an additional connection tothe outer wall) or locks it firmly in place (by pressing it against theinner wall).

The introduction sleeve is preferably made of medical grade steel. Allphysiologically tolerable materials of high strength and resistance are,in general, suitable for this purpose.

In an especially preferred embodiment, the introduction sleeve is guidedthrough the hollow needle of a medical trocar to facilitate theintroduction.

The invention is hereinafter explained in more detail based on theexemplary embodiments shown in the figures.

Reference is made to the following figures:

FIG. 1 a is a not-true-to-scale representation of a vertebroplastydevice 1 with a catheter 2 prior to the introduction into the cavity

FIG. 1 b is a not-true-to scale representation of a vertebroplastydevice 1 with a ball-shaped dilated balloon implant 3

FIG. 1 c is a not-true-to-scale representation of a vertebroplastydevice 1 with a cuboid-shaped dilated balloon implant 3

The vertebroplasty device 1 shown in FIG. 1 a comprises an introductionsleeve 2 and a dilatable balloon implant 3. At the distal end of theintroduction sleeve 2, the balloon implant 3 is attached to the outerwall of the introduction sleeve 2 in a form-fit manner by hot-forming.To provide additional safety, the connection is reinforced by a clampingring designed as a stopper bead 4 that acts on the outer circumferenceof the introduction sleeve 2 to prevent any movement towards the distalend.

After establishing a percutaneous access tract and opening the vertebrausing known techniques, e.g. a trocar, the introduction aid 5, e.g. thehollow needle of the trocar, is moved up to the vertebra opening, andthe balloon implant 3 is introduced into the vertebra cavity in deflatedcondition.

In this x-ray-controlled intervention, the introduction sleeve 2 isfirst moved up to the vertebra opening. Then the balloon is introducedinto the cavity by moving the introduction sleeve 2 forward, making surethat the distal end of the introduction sleeve 2 is introduced as wellto ensure complete introduction. The intervention is x-ray-controlled,the positions of the introduction aid or catheter 5 and the introductionsleeve 2 being controllable due to the use of markers.

Subsequently a suitable filler material (polymethyl methacrylate, bonecement or another suitable, preferably x-ray-resistant material) isintroduced from outside through the introduction sleeve 2 into theballoon implant 3, placed inside the cavity, until the implant fills thecavity.

FIGS. 1 b and 1 c show two different embodiments of the implant 3′/3″,which may assume different shapes in dilated condition (ball 3′ orcuboid 3′″). Thus, depending on the shape of the cavity, an implant 3can be chosen that is designed to assume a shape that is particularlywell adapted to the form of the cavity. Moreover, due to the elasticityof the nylon material, the implant 3 when dilated will expand beyond itspredetermined shape, advancing further into the cavity, thus filling itparticularly well.

In this example, the implant 3 consists of the balloon proper. Theballoon is so preshaped that, in dilated condition, it has a neck 6(smaller outer circumference compared to the body 7) and a body 7. Inthe area of the neck 7, the implant 3 is provided with a thinner wallsection, owing to which the implant 3, after being filled with thefiller material, can be separated from outside from the introductionsleeve 2 by turning the introduction sleeve 2 to some degree whileexerting a slight pull.

The turning movement, in combination with the elasticity of the nylonmaterial 8 used for the implant 3, causes the neck 6 of the implant 3 toclose, so that no major quantities of filler material can exit towardsthe proximal end.

Moreover, suitable closing means for the cavity (e.g. plugs or bolts)may be used to close the cavity after it has been filled. Alternatively,implants may be used that are themselves equipped with closing elements(not shown).

In addition, after having performed the turning movement that bringsabout the closure of the neck 6 and separates the implant 3 (by the pullaction and a further turning movement), the surgeon may for instancewait until the filler material has hardened. Here it must be made surethat the distal end of the introduction sleeve 2 is removed from thevertebra and placed at the opening of the cavity before the hardeningprocess is complete. In this manner, it is ensured that no accidentalconnection can form between the introduction sleeve 2 and the vertebra.

In these embodiments, the introduction aid 5 is designed as a hollowneedle of a medical trocar the introduction sleeve 2, together with theimplant 3, is moved through the introduction aid 5 into the therapyposition.

First, the ensemble consisting of the introduction aid and obturator(trocar) is introduced through the skin into the bone in anx-ray-controlled process. Once the target position has been reached, theobturator is pulled out. The hollow needle now constitutes the workingtract leading to the target location. Through the hollow needle, thesoft balloon can be pushed forward into the therapy position without therisk of sticking to the bone skin while being pushed forward. (FIG. 1 aabove shows the introduction aid pushed over the hollow needle andballoon.) Once the balloon is in its target position, the introductionaid is pulled back to such an extent that the balloon can be dilated byinjecting bone cement.

The filler material and the balloon material are to be so selected toensure that 2-3% of the material exits into the cavity before the fillermaterial is hardened. This makes sure that the implant is safely placedinside the cavity without the risk of filler material getting into theposterior quarter of the vertebra and filling venous vessels in thatarea (or the risk of embolies and infarctuses being caused by freelyfloating, hardened filler material).

Depending on the configuration of the cavity, it may be expedient tointroduce several implants, using different access tracts, whereappropriate.

1. A dilatable balloon implant, characterized in that it is designed toprovide limited liquid permeability.
 2. The implant according to claim1, characterized in that a balloon of the implant is made of a materialthat provides limited liquid permeability.
 3. The implant according toclaim 2, characterized in that the material is a textile tissue orfabric.
 4. The implant according to claim 3, characterized in that thematerial is elastic.
 5. The implant according to claim 4, characterizedin that the material is a nylon tissue.
 6. The implant according toclaim 5, characterized in that the textile material conforms to DINStandard 53861-3.
 7. The implant according to claim 2, characterized inthat the material is inherently liquid impermeable and provided withpores.
 8. The implant according to claim 7, characterized in that thepores account for up to 5% of the balloon surface.
 9. The implantaccording to claim 7, characterized in that the material is stippledlatex.
 10. The implant according to claim 2, characterized in that thematerial used for the balloon has a permeability level to medical bonefiller material of 0.05 to 6%.
 11. The implant according to claim 1,characterized in that the balloon implant is preshaped in such a mannerthat it assumes a predetermined shape when dilated.
 12. The implantaccording to claim 1, characterized in that the implant is provided witha means for joining, in a separable and conductive manner, with anintroduction sleeve (2).
 13. The implant according to claim 1,characterized in that it is provided, at its proximal open end, with athinner wall area serving as a predetermined breaking point.
 14. Theimplant according to claim 1, characterized in that it is provided, atits proximal open end, with a means for closing a balloon lumen of theimplant.
 15. A vertobroplasty device equipped with a balloon havingimplant having limited liquid permeability, which is connected to thedistal end of an introduction sleeve in such a manner that the interiorof the implant communicates with the introduction sleeve lumen.
 16. Adevice according to claim 15, characterized in that the implant isjoined to the introduction sleeve by means of a form-fit joiningtechnique, such as gluing, clamping, expanding or bolting.
 17. A deviceaccording to claim 15, characterized in that the connection between theintroduction sleeve and the balloon implant is separable.
 18. A deviceaccording to claim 15, characterized in that the connection between theintroduction sleeve and the balloon implant is inseparable and that theballoon implant is provided with a predetermined breaking point.
 19. Adevice according to claim 15, characterized in that the open end of theballoon implant is attached to the inner circumference of theintroduction sleeve.
 20. A device according to claim 15, characterizedin that the open end of the balloon implant is pulled over the distalend of the introduction sleeve and attached to the outer circumferenceof the introduction sleeve.
 21. A device according to claim 15,characterized in that the introduction sleeve is provided, at its distalend, with an additional means for securing the balloon implant in place.22. A device according to claim 15, characterized in that theintroduction sleeve is made of medical grade steel.
 23. The implantaccording to claim 1, characterized in that the material used for theballoon has a permeability level to medical bone filler material of 1 to4%.
 24. The implant according to claim 1, characterized in that thematerial used for the balloon has a permeability level to medical bonefiller material of 2 to 3%.